1. Field of the Invention
The present invention relates to an automatic control apparatus for a weaving machine. More specifically, the present invention relates to on off improvement in an control apparatus for automatically stopping the operation of the weaving machine upon detection of improper shedding of the warp, such as intertwining of the wrap caused by shag thereof, suspension of snapped warp, or the like during the weaving operation of the weaving machine.
2. Description of the Prior Art
When the warp gets intertwined due to shag thereof or is snapped to be suspended during the weaving operation of the weaving machine, improper shedding of the warp is caused, which could result in a defect of the resultant fabric. Various apparatus for automatically detecting such improper shedding of the warp have been proposed. Of such prior art apparatuses, an apparatus of a type for detecting improper shedding of warp in a photoelectric manner is particularly preferred in view of the response rate of the operation thereof. Detailed disclosure of such a photoelectric detecting scheme for improper shedding of the warp is seen in the Japanese Pat. No. 773841, issued June 30, 1975 to the same assignee as the present invention, entitled "Automatic Control Apparatus for Weaving Machine", which was published for opposition Sept. 27, 1974 as Japanese Patent Publication No. 36071/1974.
FIG. 1 is a diagrammatical view showing an outline of a photoelectric detecting scheme for detecting improperly shedded warp, in which the present invention can be advantageously employed. The warp 1 and 2 undergoes the shedding motion by means of healds 3 and 4, while the fabric is woven and is transferred leftward. In FIG. 1 the warp 1' and 2' which have become intertwined with each other due to the shag is shown in the dotted line. A reed 5 is caused to make reciprocating motion by rotation of a crank shaft 6. A sleigh 7 is provided on a sleigh sword 8 and a light source 9 and a photoelectric device 10 are provided rearwardly of the reed 5 so as to be opposed to each other such that a light axis thereof penetrates the shed of the wrap. A cam 11 is fixedly provided to the crank shaft 6 such that a timing switch 12 is opened or turned off during a suitable time period of one rotation of the weaving machine, for example, during only the period when the above described photoelectric detecting scheme detects the shadow of the warp 1' and 2' which caused the improper shedding of the warp. The time period when the timing switch 12 is opened is selected to be about one seventh of one full rotation of the crank shaft 6, for example, from 80.degree. to 130.degree. of the rotational angle, or about one third to forth of one full rotation, for example, from 50.degree. to 150.degree. of the angle, in the embodiment of the present invention. The on/off operation of the switch 12 is utilized to provide a gate signal for transferring the warp detected signal obtainable by the photoelectric detecting scheme to the subsequent stage, as is more fully described hereinafter. The photoelectric detecting scheme is shown only by way of an example it is understood that many modifications for detecting the warp of improper shedding in a photoelectric manner can be implemented by those skilled in the art.
FIG. 2 is an illustration showing an detection range by means of the photoelectric detecting scheme of FIG. 1. The scheme has been implemented such that the warp of improper shedding can be detected at the range of 80.degree. to 130.degree. of the rotational angle of the crank shaft 6, (i.e., the timing switch 12 is opened by the cam 11 within the range of 80.degree. to 130.degree. of the rotational angle of the crank shaft 6). In such a situation the warp 1, which has been uppermost in the extreme shedding condition is liable not to be lined in the lateral direction, particularly in case of the fabric the warp of which is not easy of shedding in the nature thereof, with the result that some warp 1" as shown in two dotted line is liable to be suspended. The suspended warp 1" interrupts the light beam from the light source 9 at the said detection range of 80.degree. to 130.degree. and as a result a warp detected signal is obtained by the photoelectric device 10 as if improperly shedded warp were detected, notwithstanding the proper shedding of the warp in such a situation. As a result, the weaving machine is erroneously stopped automatically as if the warp of improper shedding had been detected, notwithstanding the proper shedding of the warp.
In order to avoid such a problem, those skilled in the art might think that the detection range and thus the opening range of the timing switch 12 should be shifted by 10.degree., for example, to 90.degree. to 140.degree. in terms of the rotational angle of the crank shaft 6. In fact, it might be possible that the chance of malfunction in response to the suspending warp 1" is reduced which is particularly caused in case of the warp not easy of shedding. Nevertheless, it is necessary to change the angle and shape of the cam 11 with respect to the shaft in order to adjust the opening time period of the timing switch 12, although such change is extremely difficult. Assuming that the detection range is set to be 90.degree. to 140.degree. from the beginning, then another problem is encountered that weaving with undesired raised portion is liable to be caused in case of the fabric of ordinary warp in the nature.